TBI Adjustable Pressure Mod

[JeepsAndGuns]

You say the map sensor is hooked to a vaccume port on the intake? If so, then it sounds like someone in the past had them off at one time and simply put them back on incorrectly. Attach the map sensor to that port on the rear of the tbi and hook the vac hose thats running all that other stuff to the intake port.

[Six_Shooter]

Using a port directly off the manifold will result in the same reading as the proper port on the TB. Manifold vacuum is manifold vacuum.

[EagleMark]

Pictures here may help.
viewtopic.php?f=9&t=21

[mudbuggy]

More I think about it, it makes me wonder if that's the reason the cruise won't work. I need to move the map anyways, the closer it is to the vacuum source the quicker it will tell the ecm what to do. I think I can get rid of a foot and a half of vacuum line. I'll just make a bracket to mount the map on the firewall, might even mount it on the air cleaner housing just to try and keep the line as short as possible.

[Six_Shooter]

More I think about it, it makes me wonder if that's the reason the cruise won't work. I need to move the map anyways, the closer it is to the vacuum source the quicker it will tell the ecm what to do.

Really? Since vacuum is more like a fluid than flowing air, the change in pressure happens very quickly over a long distance.

I've mounted MAP sensors inside the passenger compartment, and had no noticeable lag or issues with the long (about 3') of tube between the TB port and the MAP sensor.

[EagleMark]

He's right, just have to get good vacuum line! Notice he said tubing, like what comes on a Chevy to begin with. Don't want cheap/wrong vacuum hose to collapse or kink!

I know one rule that came from Detroit engineer was MAP should be very close to MAP vacuum port level. Meaning same height. I don't know why but have never tried any other way. Where your MAP is, is where it came from GM. No need to change location.

[mudbuggy]

Just going by my mechanics at my shop on the map
. They were saying that the closer the better and that's why the are mounted on the intakes now adays. They also stated that the tbi stuff is not what they are dealing with daily

How many tps styles are there for the 'truck' series? Are they (the tps) interchangeable on all of the tbi units? Reason I ask is the tbi I am rebuilding doesn't have the same plug ( 3 prong micro pointed toward the ps fender) as the tbi that's on the truck ( 3 prong weatherpack style pointed toward the hood). No I haven't compared to two, it was raining and I didn't want to float away. Thanks guys

[EagleMark]

Three that I know of on TBI. 3 prong oval pointing up and three prong oval out are interchangable. The 3 prong round is not. You will have to repin a new plug onto your harness.

There are also 2 differant IAC and the small block, big block have 2 wires changed.

MAP on the intake may be better when it gets down to micro engeneering, but won't change a thing on your truck. Also most newer cars that have AMP mounted on intake only use it for a split second between key on and crank to get Barometric reading. Then they run off MAF.

[mudbuggy]

Holy shit was that a pita. I switched out the units, at least the upper housings, and then I couldn't get any pressure. Took it apart, made sure that the regulator baffle was sealed, retightened the upper housing and tried again. Still leaking. Well maybe a half a dozen tries later, I finally figured out that the replacement spring isn't strong as the oem spring. So I cleaned up the oem unit and put it back on. I now have 10.5 psi, apparently I had a small leak, where I was loosing 1.5 psi constantly!!! 10.5 is with the oem regulator, and I can't move the bottom of the regulator to attempt to adjust it. I did try, even dripping with gas and brake cleaner I thought about heating it up just for a second. I just went out and looked at it, it's still dry, it was always damp around the bowls and down the back of the tbi unit. Now I just need a replacement spring and I can redo my redone regulator. Yea!!!